From the prior art, for example the patent application DE 2014 102 202 52 A1 is known. Said document concerns a method for carrying out a parking brake process in a motor vehicle with an automated parking brake, wherein the parking brake process comprises at least two phases, wherein in a first upstream phase no clamping force is established by the parking brake, and in a second downstream phase a clamping force is established by the parking brake, wherein the parking brake comprises an actuatable parking brake actuator for producing the clamping force, characterized in that the detection of a transition from the first phase to the second phase is carried out based on a time profile of a specific parameter of the actuation of the parking brake actuator. In this case, the determination of the transition from a zero-force phase to a force establishment phase is also carried out during a parking brake engagement process.
New requirements are placed on the parking brake by functions such as highly automated parking (the driver is not sitting in the vehicle). In the event of a malfunction of the hydraulic brake device (for example of the ESP), the parking brake acts as the necessary (for safety reasons) fallback level. Investigations have revealed that to meet the safety-related requirements in this case an actuation time of 200 milliseconds is necessary. Said value can however vary in the range of 100 ms≥t≤700 ms because of altered requirements. The actuation time means in this case the time that elapses when the actuator is energized until ultimately the establishment of a clamping force takes place. However, this is not currently possible, or is only possible at great technical cost, with the solutions that are customary in the market.